Method of preparing thiophosphorylchloride



2,715,551 Patented Aug. 16, 1955 NIETHOD OF PREPARING THIOPHOSPHORYL- CHLORIDE Florian F. Knotz, Graz, Austria No Drawing. Application October 2, 1953, Serial No. 383,935

8 Claims. (CI. 23-44) This invention relates to an improved method of making thiophosphorylchloride by the reaction of sulfur and PCla. Sulfur does not combine with PCI; under ordinary conditions. However, it was found that the reaction was catalyzed by the presence of anhydrous AlCla, Knotz, Oesterr. Chemiker Zeitung 50, 128 (1949). Although AlCl3 effectively catalyzes the combination of S with PCl3 under ordinary conditions, efforts to employ Al metal in conjunction with halogen have heretofore been unsuccessful.

In accordance with the present invention it has been discovered that reaction of S and PCl is catalyzed by either Al or Fe in the presence of bromine or chlorine providing a trace of iodine is also present. The metal should be finely divided. In the case of powdered iron it should be free of considerable amounts of FeO, FezOz and Fe(OH)3. Reduced iron is also satisfactory. The proportion may vary but about 3% on the PCl3 has given excellent results. The iron can be used repeatedly to catalyze the desired reaction but it should be employed immediately for this purpose. Similarly, in the case of Al powder the results depend upon the quality used. Very pure and very finely divided Al requires less iodine than with inferior grades. About 1% Al powder on the PClz has given good results although this proportion is subject to variation. Mixtures of Fe and Al powder are also intended.

It is advantageous to mix the metal powder, bromine and iodine with sulfur a short time before adding the PC13. Bromine in the range of 0.83% and iodine in the range of 0.2O.8% on the PCl have given excellent results. Iodine never can be replaced by any other halogen, whereas chlorine may be used instead of bromine. In this case a cold saturated solution of PCla with C12 is employed together with the other catalysts (Fe and I2 or Al-l-Iz or a mixture of Fe-l-Al and I2) in order to combine the PCls with sulfur. Increasing the proportion of I2 shortens the reaction time up to a certain degree. Conversely, decreasing the proportion of i2 necessitates a higher proportion of Br2 for comparable results. However, the yields are generally not affected, providing enough iodine is employed to start the reaction. All of the catalyst components with the exception of Al can be recovered and reused in subsequent reactions. The metal can be recovered by filtration or left with the heel from distillation of the crude reaction products. Any bromine and iodine contained in the PSCl3 can be removed by treatment with cold dilute NaOH and recovered in known manner.

The catalyst combination described effects combination of S and PCl3 under atmospheric pressure at refluxing temperature of the reaction mixture. The use of pressure equipment is therefore obviated. A trace of iodine is sufiicient to initiate reaction. When Al powder is used, the reaction takes place with the evolution of considerable heat. Employing Fe powder, the reaction never becomes vigorous so that it is necessary to continue heating until the reaction is complete. Fe powder has the advantage that the reaction goes smoothly without the danger of explosions which may occur by using Al powder or AlCla in higher amounts.

The following examples illustrate the invention in detail but are not to be taken as limitative thereof.

Example 1 Into a reaction vessel of suitable capacity fitted with a reflux condenser there is mixed 24 parts by weight of sulfur, 3 parts by weight of fine iron powder or reduced iron, 0.2 part by weight of iodine and 3 parts by weight of bromine in the order named. After about 5 minutes 100 parts by weight of PCl are added and the mixture heated to refluxing temperature. The reaction is nearly complete after an hours refluxing and complete after heating another minutes. The iron powder is removed by filtration and used immediately for the next run. The crude PSC13 is distilled to yield 116 parts by Weight, boiling range 124-127 C. The product is t; treated with an ice-cold solution of 109 cc. of Ill-12% vNaOH.

The layer consisting of PSC13 is separated and dried with CaCl or Na. A second distillation yields 112 parts by weight of PSCls, B. P. 124-126 C. A second distillation is not necessary as the product is essentially pure after drying. The catalysts are recovered from the residue after the first distillation by treating with 100 cc. of a warm -25% solution of NaOH. These caustic solutions may be used to recover catalysts from other runs until the NaOH is exhausted. The solutions are then united, the water evaporated and the Bra and I2 recovered by one of the usual methods.

Example 2 Into a reactor of suitable capacity fitted with a reflux condenser and stirrer there is charged 24 parts by weight of powdered sulfur, 3 parts by weight of fine iron powder or reduced iron, 0.8 part by Weight of iodine and 2 parts by weight of bromine, the additions being made in the order named. The mixture is allowed to stand for a short time and then 100 parts by weight of PCl3 is added. The mixture is then heated to boiling for about minutes at which time the reaction is complete. The end of the reaction can be observed when no more PCl3 is condensed in the reflux condenser and iodine vapors are seen in the flask. Isolation of the product as described in Example 1 yields 110 parts by weight of PSCl3, B. P. 124126 C.

Example 3 A mixture of 24 parts by weight of sulfur, 3 parts by weight of iron powder, 0.7 part by Weight of iodine and 2 parts by weight of bromine is prepared as described in the foregoing examples. After a few minutes parts by weight of PCl are added and the mixture heated to boiling. After heating for an hour substantially all of the PCls is converted into PSCla. Isolating the product as described in Example 1 yields 108-110 parts by weight of PSClg, boiling range l24126 C.

Example 4 A mixture of 24 parts by weight of sulfur, 3 parts by weight of iron powder, 0.6 part by weight of iodine and 2 parts by weight of bromine is prepared as described in the preceding examples. After a short time 100 parts by weight of PCl3 are added and the mixture heated to boiling. A reaction period of 1 /2-2 hours is sufllcient to convert substantially all the PCls to PSC13. Isolation of the product as described in Example 1 yields 114 parts by Weight of PSClz, boiling range 124-126 C.

Example 5 The reaction mixture described in Example 4 is preweight of PC13.

remove iodine, and other impurities.

V V :The residue of the first iodine recovered in the usual way.

7 iodine, 1 part by IboilingJ The foam on 'brown but gradually turns to violet and then after about 3' paredwith'the difference that the mixture of sulfur, iodine, bromine and iron powder is gently heated before adding PCls. The mixture becomes hot and iodine vapors are visible in the flask. When the mixture has nearly cooled to room temperature the PCl3 is added and the reaction is carried out in the usual way by heating for an hour and -l5 minutes. Isolating the product as described in Example 1 yields 110-112 g. of PSC13, boiling range 124-126 C.

. 7 Example 6 Into 'a reaction vessel fitted with reflux condenser there is mixed 5 parts by weight of sulfur, 0.6 part by weight Fe powder, 0.1 part by weight iodine and 20 parts by The mixture is heated gently so that all of the iodine has dissolved. After cooling to room temperature there is bubbled in a stream of dry chlorine. The violet color of the mixture disappears. When the PC13 is saturated with chlorine the mixture is heated to refluxing temperature. After some time the violet color of the iodine gradually appears again and after 2-3 hours the reactionis complete. The iron is removed by filtration and immediately used forthe next run. The

crude PSCl3 is distilled and the distilled product treated with an ice-cold solution of dilute NaOi-I in order to After separating the PSClz and drying it with CaCla, the distillation yields 18-19 parts by weight PSC13, boiling range 124-127 C. distillation is treated with a concentrated solution of NaOH which may be used for treating the residues of other runs until the NaOI-I is ex- Lil hausted. Then the caustic solutions are united and (NoTE.Dont bubble chlorine into the boiling mixture because of the following equation: 2PSCl3+Cl2- 2PCls+S2Cl2. See: Gmelin Krautt Handbuch der anorganischen Chemie, I, 2, Seite 192, 7. Auflage (1909).)

Example 7 Into a reactor of suitable capacity fitted with a reflux condenser is charged '24 parts by weight of sulfur, 1

part by, weight of Al'powder, 0.3 part by weight of weight of bromine and 100 parts by The reaction mixture is heated to the boiling mixture is initially weight of P613.

minutes the. color gradually disappears, becoming colorlessrafter 30 minutes. After about 45 minutes the reaction becomes quite violent but can be easily con trolled by cooling With water or ice water. The reaction is complete within a few minutes. The reaction mixture is filtered to separate theAl powder and his used immediately for the next run. Purification of the PSCls as described in Example 1 yields 106-108 parts by weight, boilingrange 124-126 C. 7

Example 8 Into a reactor of suitable capacity is charged 12 parts by weight of sulfur, 0.8 part by weight of bromine, 0.2.

part by weight of iodine, 1 part by weight Al powder and 50 parts by weight of PCls. A vigorous reaction sets in at the boiling point of the PCl: which is terminated withina few minutes but the yield is lower with this 7 higher proportion of catalyst due to side reactions.

Example 9 heating continued for about minutes or until the violet color of the foam disappears and a vigorous reaction sets in. The reaction is complete within a short time. Isolation of the product as described in Example 1 yields 107-110 parts by weight of PSCls, boiling range 7 Example 10 into a reactor of suitable capacity fitted with a reflux condenser is charged 5 parts by Weight of sulfur, 0.2

part. by weightAl powder, 0.1 part by weight of'iodine and 20 parts by Weight heated until all iodine has dissolved. .After cooling to room temperature there is bubbled in a dry stream of Clz until the violet color of the mixture has disappeared completely and the reaction mixture becomes slightly warm. When heating the mixture the violet color of the iodine appears again at the B. P. of PC13. After refluxing minutes the mixture becomes colorless and after minutes a vigorous reaction sets in which is complete in a few minutes. Cooling with ice water is necessary when the reaction starts. has cooled to room temperature there is added 4.4 parts by weight of sulfur, and 20 parts by weight ofPCl-a The mixture becomes warm and after refluxing 15-30 minutes the reaction is complete-without getting violent.

The crude PSC3- is distilled directly from the flask and. yields 42-44 parts by weight of PSCh, B. P. 122-123 C. The product contains traces of iodine and has, therefore, a pink color. Iodine may be removed from the PSCls by treating with an ice coldsolution of dilute NaOl-I, from which iodine can may be redistilled but it is quite pure after drying :with CaClz. hard after cooling. with water, evolving H28. evolves violet iodine vapors. also can be regained. 7

It decomposes violently when treated \Vhen heated the residue Example 11 Example 12 For the initial charge in Example 10 there is substituted 5.0 parts by weight of sulfur, 0.2 part by weight Al powder, 0.05 part by weight of iodine and 20 parts by weight of PCls, otherwise the 'procedure and quantities employed are the same as in ExamplelO. The

reaction mixture becomes colorless after -40 minutes and after 45 minutesa vigorous reaction takes place.

' Continuing as in Example there is obtained 42-44 parts by weight of PSCls (iodine containing) 3. P. 12.3- 124 C. I

Although an excess of the metal is advantageous in order to facilitate the formation of the unknown'catalysts, the experimental evidence indicates that only small amounts, in the case of aluminum, and traces, in

respect to iron, participate in the reaction. Strongv heating of the boiling PCla is advantageous in order to shorten the reaction time. During the heating nearly all of the aluminum is converted into unknown compounds so it cannot be conveniently regained. The unknown compounds formed are not; capable of catalyzing a new reaction of PCls and sulfur.

t is intended to cover all changes and modifications" of the examples of the inventionherein' chosen for purposes of disclosure which do not constitute departures from the spirit and scope of the invention.

of PC13. The mixture is gently After the mixture.

be regainedl The PSCl3 The dark residue after the distillation'becomes From this residue iodine The procedure is the sameas in Ex- Vwhat is claimed is:

l. A method of preparing PSCIs which comprises reacting PCls with sulfur in the presence of a catalyst mixture comprising a member of the group consisting of chlorine and bromine and mixtures thereof and a menr ber of the group consisting in iron powder, aluminum powder and mixtures thereof said catalyst mixture also including a trace of iodine.

2. The method of claim 1 in which the reaction is carried out at refluxing temperature.

3. A method of preparing PSC13 which comprises reacting PCla with sulfur in the presence of a catalyst mixture comprising per 100 parts of PC13, about 3 parts powdered iron, 2-3 parts bromine and 0.2-0.8 part iodine.

4. A method of preparing PSCla which comprises reacting PCls with sulfur in the presence of a catalyst mixture comprising per 100 parts of PC13, about 1 part aluminum powder, 0.8l.0 part bromine and 0.20.3 part iodine.

5. A method of preparing PSCL: which comprises reacting PCl3 with sulfur in the presence of a catalyst mixture comprising a mixture of iron and aluminum powder, bromine and iodine.

6. A method of preparing PSC13 which comprises reacting PClg with sulfur in the presence of a catalyst mixture comprising per 100 parts of a cold solution of PCl3 saturated with chlorine, about 3 parts powdered iron and about 0.5 part of iodine.

7. A method of preparing PSClz which comprises reacting PCl3 with sulfur in the presence of a catalyst mixture comprising a cold saturated solution of PC13 with chlorine, aluminum powder and iodine.

8. A method of preparing PSC13 according to claim 6 in which the crude PSCls, containing the catalyst, is able to convert a new charge of PCl and sulfur into PSCls.

References Cited in the file of this patent UNITED STATES PATENTS 2,575,316 Jonas et al. NOV. 13, 1951 2,575,317 Jonas et al Nov. 13, 1951 2,591,782 Cook Apr. 8, 1952 

1. A METHOD OF PREPARING PSC13 WHICH COMPRISES REACTING PC13 WITH SULFUR IN THE PRESENCE OF A CATALYST MIXTURE COMPRISING A MEMBER OF THE GROUP CONSISTING OF CHLORINE AND BROMINE AND MIXTURES THEREOF AND A MEMBER OF THE GROUP CONSISTING IN IRON POWDER, ALUMINUM POWDER AND MIXTURES THEREOF SAID CATALYST MIXTURE ALSO INCLUDING A TRACE OF IODINE. 